This blog follows and explains the processes behind interesting geological events. The emphasis is on those events that are energetic, explosive, and have led to, or have the potential to lead to, disasters.

Welcome!

This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Wednesday, April 6, 2011

Landsat image of Lituya Bay
as presented in the Geology.com article referenced in the text

Often referred to as "the largest tsunami" ever recorded**, a wall of water 1720 feet high surged over a spur of land at the head of Lituya Bay, Alaska, following a rockslide at the head of Lituya Bay, Alaska. This rockslide was triggered by the magnitude 7.7 Alaska earthquake on the July 9, 1958. An excellent summary and collection of photographs can be found at Geology.com. This report is based on the U.S.G.S. Professional Paper 354-C, "Giant waves in Lituya Bay, Alaska, 1960" by Don J. Miller. Miller had been working in the area documenting evidence for at least four large waves previously, estimated to have been in 1936, 1899, 1874 and 1853-54. The discoverer of Lituya Bay, the French explorer, LaPerouse, noted the lack of trees and vegetation on the sides of the bay in his ship log, commenting that it looked "as though everything had been cut cleanly like with a razor blade."(Reference from here, which also contains an excellent discussion of the event and of possible mechanisms of origin of the wave).

Lituya Bay and the elevations of the wave
from Geology.com based on Miller's USGS PP (1960)

As illustrated in the second figure here, the Fairweather Fault trends nw-se across the head of the Bay, giving it a T-shape. The weaker fault material has been scoured by glaciers to produce the Fairweather Trench along the fault zone. The earthquake was centered on this fault zone. A rock slide at the head of the bay (red zone in the second figure) fell from an elevation of about 3000 feet (914 meters); its volume was about 40 million cubic yards (30.6 million cubic meters). (Assuming no resistance from either air or rock that it was sliding along, this highest part of the rockfall would have hit the ground at nearly 300 miles per hour, or 133 meters/second. The center of mass was at about 2000 feet so the average velocity about 240 miles per hour.)

The impact from this rockfall on the water generated a huge splash wave within Gilbert Inlet. The impact of this rock mass disturbed not only the water, but also the sediments under it, and also tore off part of the toe of Lituya Glacier, causing drainage of a subglacial lake. The "tsunami height" of 1720 m is taken from the height that "this impact splash" reached on the ridge at the southwest side of Gilbert Inlet, in close proximity to the point of impact. As the splash traveled out into Lituya Bay, it quickly decayed to less than 200 feet high, and maintained a height on the order of 100 feet throughout much of its passage down the Bay.

Remembering that the word "tsunami" means "harbor wave," this wave in Lituya Bay qualifies as a "harbor wave." It is may be the best studied example of the near-field dynamics of a big splash. Astrogeologists would also call it "impact ejecta." Further technical references are given at the end of this article.

**An example this wave being called a tsunami is the BBC Nature program Mega Tsunami-Alaskan Super Wave--Amazing Survival."

No comments:

This Blogger is a Happy Camper!

Click photo for a bio/CV

==>My book:The Dynamics of Disaster <==

Published by W.W. Norton--Click on image to go to Amazon.com

Synopsis of Book and Reviews

If you want to learn a bit of the science behind earthquakes, landslides, volcanic eruptions, tsunamis, rogue waves, cyclones and hurricanes, and tornadoes, this is an introduction that weaves together stories of various disasters--some barely known to much of the world--their causes and dynamics, and some suggested actions we can take to protect ourselves. The book is available both in paper and as an audio CD.

"This is a fantastic book. I've recommended to colleagues at FEMA and am using it as a text for my disaster classes. It really demonstrates how knowledge of the environment should inform policy. It was a page turner for me!"--Dr. Trish on Customer Reviews at Amazon.com

''Geologist Kieffer argues that we don't understand disasters as well as we should. She contrasts 'stealth disasters' caused by long-term human impact, including climate change and soil erosion, with natural disasters or 'acts of God,' which are also increasingly affected by human actions . . . [A] highly accessible look at disasters.'' --Booklist

"Kieffer's brisk and lucid presentation has some of the relish with which surgeons reputedly regale each other with tales from the operating theatre. Laid out before the reader are the suppurating wounds, scalds, tremors, and scars acquired by the Earth over millennia, centuries, decades, or minutes."--Claudio Vita-Finzi in The Times of London

"If you are an amateur weather geek, disaster wonk or budding student of the earth sciences, you will want to read this book. (If you're squeamish, skip the chapter titled "A Plague of Snakes.")--Seattle Times by Mary Ann Gwinn

"[T]he clarity of Kieffer’s writing, coupled with her careful choice of supporting graphics, makes the content engaging and accessible to a wide readership." Alison Stokes in TheTimesHigherEducation

“In The Dynamics of Disaster, famed geoscientist Susan Kieffer merges stories and science in a fascinating introduction to the dangerous side of the Earth, with key insights for citizens and enough excitement to captivate the full range of students.”—Richard B. Alley, author of Earth: The Operator’s Manual

"Both general readers and working scientists will enjoy this well-written book--and learn some things they did not know...Summing up: Highly recommended. Lower-division undergraduates through professionals; general audiences."--by Seth Stein in Choice Reviews Online (of the American Library Association), April 2014

"This [impressive] book ought to be placed in the hands of politicians, engineers, insurance assessors and, frankly, anyone who sees sense in understanding the processes and systems that guide our planet." --Geographical, December 2013, by Jonathan Wright

This book is part of a recent trend--one that is just beginning, but is likely to grow--in which scientists, especially young ones, seek to move beyond the "disasters are bad" view presented in beginner classes to a more sophisticated and nuanced view…Seth Stein in Physics World (U.K.)

"It is like a "Magic School Bus" outing for adults, with Kieffer acting as Ms. Frizzle, guiding the reader around the world to disaster hotspots, where she analyzes and breaks down the physical characteristics that contribute to events in those areas."--Summit Daily, December 20, 2013

#1 in list of Best Sellers: Geology, from May 2013 to March 2014. LibraryJournal.com

Victoria Raschke's Reviews (Jan. 09, 2019) Kieffer's explanations of the how natural disasters occur is perfectly suited to the interested layperson. The section on rogue waves was worth the price of admission in that it explains something that always seemed kind of supernatural. If you have any interest at all in understanding our living planet and why it sometimes feels like it would be happy to be rid of us, this is the book for you.